As a radiation medical treatment apparatus for cancer and others using electron beam and X-ray generated therefrom in Prior Art Example 1, a linear accelerator (LINAC) is mainly used at present in which electron is accelerated to the energy of several to higher than ten MeV, for example, Japanese Laid-Open Publication (JP H10-64700A (1998), p. 4, FIG. 1). Also as a linear accelerator, a microtron electron accelerator is known, for example, in the Japanese Laid-Open Publication (JP H07-169600A (1995) pp. 2–3, FIGS. 1 and 2).
FIG. 20 illustrates an example of makeup of a medical treatment linear accelerator of Prior Art Example 1. The medical treatment linear accelerator 100 comprises an electron gun 101, an accelerating device 102, and a magnetic bending apparatus 103 provided outside of the accelerating device 102. The electron input into the accelerating device 102 by the electron gun 101 is accelerated along the beam axis of the accelerating device 102. The accelerating device 102 is made up of a microwave cavity for acceleration, and connected to a microwave oscillator 104 and its control circuit 105. The microwave oscillator 104 generates the electromagnetic field in the accelerating cavity of the accelerating device 102. When an electron passes the accelerating cavity of the accelerating device 102, it is focused by electromagnetic field of microwave, and is accelerated. The thus accelerated electron beam 106 is irradiated from an output window 107 to become an output electron beam 108, and used for radiation medical treatment.
The orbital of said output electron beam 108 is changed by the magnetic bending apparatus 103, and it is irradiated onto such target 109 as gold or tungsten that generates X-ray, so the X-ray beam 110 can be generated. Said X-ray beam 110 is also used for radiation medical treatment. The size of said accelerating device 102 is necessarily about 2 m for accelerating electron beam to 10 MeV, for example, refer to the Japanese Laid-Open Publication (JP 2001-21699A, p. 2).
As another radiation medical treatment apparatus for cancer and others in Prior Art Example 2, there is a heavy particle beam accelerator. The heavy particle beam accelerator has high energy, so that it can irradiate the limited cancer organism compared with the linear accelerator by electron beam and X-ray of Prior Art Example 1, thereby has an advantage of smaller damage to normal organism, for example, refer to the Japanese Laid-Open Publication (JP 2002-110400A, p. 1–2).
As an accelerator of Prior Art Example 3, there is a fixed field alternating gradient accelerator (FFGA accelerator) proposed by Ohkawa of Japan in 1953, for example, refer to Reference (C. Ohkawa, Annual Report of Physical society of Japan, 1953). An FFGA accelerator is characterized to use a so-called alternating gradient electric magnet having zero chromatic aberration on the gradient of such particles as electron beam, and to need no change of magnetic field along with acceleration, like conventional synchrotron accelerators, thereby to be able to use fixed magnetic field. Therefore, particles can be accelerated faster.
However, an FFGA accelerator has difficulty in realization of accurate magnetic field distribution on the technological level of the time of proposal for realization of an alternating gradient electric magnet, and in recent years at last the design and test making of an FFGA apparatus for proton acceleration for the study of subatomic and atomic nuclear physics, for example, refer to References (Y. Mori et al, “FFAG (Fixed-field Alternating Gradient) Proton Syncrotron”, 1999, The 12th Symposium on Accelerator Science and Technology, pp. 81–83, and Yuzuru Nakano and KEKFFAG Group, “150 Mev Fixed Field Alternating Gradient (FFAG) Accelerator”, September, 2002, Study of Atomic Nucleus, Vol. 47, No. 4, pp. 91–101). The noise reduction technology in the FFGA electron accelerator using a betatron accelerating apparatus is disclosed in Japanese Laid-Open Publication (JP 2003-159342A, pp. 1–2). Said noise reduction technology is to generate from a speaker the sound to cancel the noise from the FFGA electron accelerator, and not to kill the noise from the FFGA electron accelerator itself.
Since the beam intensity of the LINAC of Prior Art Example 1 is as small as several hundred μA, there are such problems as that it takes long time for radiation medical treatment for cancer and others resulting in the patient's burden, causes deviance of irradiation field by breathing movement, and it is difficult to irradiate concentrating to such sick part as cancer organism. Thus, the medical treatment by electron beam and X-ray is difficult to irradiate limited to the cancer organism, compared with the cancer treatment apparatus using heavy particle beam of Prior Art Example 2, and causes bigger damage to the normal organism.
Further in the LINAC of Prior Art Example 1, since electron beam can not be accelerated upon setting the target to generate X-ray in the microwave cavity accelerating electrons, the electron beam can be used only by taking out of the accelerator. Also in the LINAC of Prior Art Example 1, since X-ray is generated by taking out electron beam from the accelerator, it is necessary to set up a radiation shield so not to damage the user's health, as the radiation is irradiated, thereby the setting costs much. Also in the LINAC of Prior Art Example 1, since a microwave oscillator of high output power is required to obtain required acceleration voltage, only a microwave oscillator of pulse motion can be used, and continuous wave (CW) operation is not possible.
On the other hand, in a radiation medical treatment apparatus for cancer and others using heavy particle beam of Prior Art Example 2, the length of an accelerator is 10 to several of tens m compared with 2 to several m of an electron beam accelerator, and the weight exceeds 100 tons. The cost is also 100 times as much as an electron beam accelerator, resulting in a problem that ordinary hospitals in general can not afford easily. Further, the accelerator of prior art needs a big high frequency cavity of the length in m unit of extremely high frequency (several GHz). Therefore, it results in the problem that the processing technique of extremely high level and accuracy is required, resulting in high manufacturing cost.
Although the FFAG accelerator of Prior Art Example 3 is that with higher beam current compared with those of Prior Art Examples 1 and 2, and capable of quick repetition, there is still a problem that such an accelerator has so far not been realized as to have the acceleration voltage of higher than about 10 MeV required for radiation medical treatment, and to be set up easily in ordinary hospitals in general, and noise of audible frequency is generated from the accelerating apparatus and others to be used for acceleration.